The present invention relates to apparatus for hard facing of machine parts, and more particularly to apparatus for hard facing of the seating surfaces of internal combustion engine valves with heat-resistant alloys.
The term "seating surface" is used to denote a chamfer made in the valve head of an internal combustion engine and used to ensure a close fit with the respective seat chamfer.
The seating surfaces of valves for internal combustion engines are subjected to repeated contact loads and to the effect of high temperatures reaching 800.degree.-1000.degree. C. Heat-resistant alloys are welded on the seating surfaces of valves to increase the service life thereof.
At present, the seating surfaces of the valves for internal combustion engines are hard-faced with the aid of apparatus comprising flame hardening, plasma-arc and HFC working elements, respectively, which are used for melting the heat-resistant alloy being faced. The adaptability for automatic operation as well as the simplicity of the process of hard facing of the valve seating surface in the HFC field are advantageous features of the apparatus with the HFC working element, as compared to other known apparatus.
Known in the art are apparatus for hard facing of the seating surfaces of valves, such as disclosed in British Pat. No. 743,582, in which the valve is assembled, i.e. the alloy ring is fitted on the valve head, and after being assembled, is placed into the fusion zone by an operator. However, much time and labour spent on these auxiliary operations predetermine low efficiency of such apparatus.
There is also known in the art an apparatus for hard facing of valves for internal combustion engines, as disclosed in the description of the invention of the USSR Inventor's Certificate No. 292,400, in which the valve is assembled and conveyed to the fusion zone (to the heater) automatically. This apparatus comprises a support movable along the vertically positioned valve stem and adapted to receive an alloy ring and feed it onto the valve stem, hinged gripping jaws provided with a mechanism for bringing them apart and adapted to clamp the valve stem end with said alloy ring thereon, said jaws being connected with the horizontal shaft of a manipulator which is adapted to turn said jaws in two mutually perpendicular planes, the valve stem being upwardly directed at the same time, thus providing for conveying said valve to the fusion zone in which there is a heater in the form of a high frequency ring-shaped electrical inductor.
This support is made as a drum freely fitted on a vertical shaft, said drum containing on its lower end face a roller interacting with a positive slide block. Another drum rigidly fitted on the same shaft is adapted to receive the valves with their stems directed downwards said valves being fed by way of a feed chute. These two drums are coaxially mounted on a vertical shaft and make up a mechanism for assembling the valves with the heat-resistant alloy ring thereon.
Though the above-described apparatus provides for automatic assembling of the valve with the alloy ring thereon and conveying said valve to the welding or fusion zone, the apparatus still suffers from a number of disadvantages.
Thus, to gear the shafts in the known apparatus use is made of Geneva mechanisms and a system of cams which substantially complicates the design of the apparatus as a whole. Besides, the described above mechanism for assembling the valve with the alloy ring thereon necessitates separate operations of putting the ring on the valve stem and subsequent conveying it to the manipulator which finally puts the alloy ring on the valve head. This in its turn complicates the design of the mechanism and reduces the efficiency of the process.
It should also be taken into account that excessive number of components significantly raises the manufacturing cost of the apparatus, as well as impairs its operating reliability.
It is, therefore, an object of the invention to provide an apparatus for hard facing of the seating surfaces of internal combustion engine valves, which is simple in construction and easy in operation.
Another object of the invention is to provide an apparatus for hard facing of the seating surfaces of internal combustion engine valves, which exhibits high operating efficiency.
Still another object of the invention is to provide an apparatus for hard facing of the seating surfaces of internal combustion engine valves, which is reliable in operation.
Yet another object of the invention is to provide an apparatus for hard facing of the seating surfaces of internal combustion engine valves, which is fairly cheap to manufacture.
These and other objects of the invention will become apparent from the detailed description of the invention.